In recent years, various driving support systems such as night vision systems and a marking light have been developed and put to practical use. In general types of driving support systems, an infrared camera can be provided to detect surroundings while illuminating the surroundings with infrared rays. When the system adopts a far infrared camera, the cost thereof can be expensive. In contrast to this, when a system adopts a near infrared camera utilizing near infrared rays for illumination, the system cost can be appropriately lowered.
In such a driving support system utilizing a near infrared camera and a near infrared illuminator, the optical axis of such a near infrared illuminator must or should be adjusted so as to form a light distribution pattern by the near infrared rays in an appropriate direction and at a certain position.
The near infrared rays emitted from such a near infrared illuminator are different from white light projected from a conventional headlight unit, but are invisible light which cannot be visually recognized. Therefore, an optical axis of such a near infrared illuminator cannot be adjusted with a common headlight tester (see, for example, Japanese Patent Application Laid-Open No. 2001-13039), which is conventionally used for optical axis adjustment. Further, to develop an optical axis adjusting device dedicated for near infrared rays may not be desirable because the system cost cannot be absorbed in view of the market size of near infrared illuminators.
Further, a general light distribution pattern formed by a common near infrared illuminator does not include a bright/dark boundary line such as a cut-off line in a light distribution pattern of a low beam formed by a headlight. In this context, it is difficult to grasp the direction and position of such a light distribution pattern formed by a common near infrared illuminator in the first place. Therefore, the optical axis adjustment with a high accuracy is difficult to be achieved.